Thermostatic mixing valves (TMVs) are well established and serve to provide a fluid (e.g., water) supply at a desired temperature. TMVs, also referred to as temperature-activated mixing valves, have a temperature responsive thermostat element, or thermal motor, operatively coupled to a valve member controlling fluid flows through hot and cold inlet ports of the valve. The mixed fluids are caused to impinge upon the thermal motor, which in turn expands and contracts and controls the relative proportions of hot and cold fluids passing through the valve. Consequently, when there is an undesirable rise in the temperature of the mixed fluid the thermal motor expands to cause the valve member to reduce the hot flow via the hot inlet port and increase the cold flow via the cold inlet port. Expansion of the thermal motor, therefore, restores the fluid supply temperature condition to that desired, with a converse operation when there is contraction of the thermal motor due to a fall in the mixed fluid temperature.
Prior art TMVs that can be used with emergency drench shower stations and eyewash stations are shown in U.S. Pat. Nos. 5,011,074; 5,379,936, 5,647,531; 6,575,377; and 6,732,937. These prior art TMV's allow a cold-water bypass upon failure of the hot water supply so that emergency drench shower stations and eyewash stations remain supplied with water even upon failure of the hot water supply.
What is still desired is a new and improved TMV that can be used to mix hot and cold water supplies to produce tempered water for emergency drench shower stations and eyewash stations. Preferably the thermostatic mixing valve will be adapted to allow a cold-water bypass upon failure of the hot water supply so that emergency drench shower stations and eyewash stations remain supplied with water even upon failure of the hot water supply.